System Databases
SingleStore has several internal or "System" databases (views):
cluster: Stores cluster-level metadata that is replicated to all nodes in the cluster. This includes information about nodes host/ports etc. and information about databases and database partitions). Cluster replicas (named something like:cluster_{uint64_t}) are created during DR (disaster recovery) cluster-to-cluster replication.information.schema: Read-only. A large set of system tables containing metadata about clusters and all the components within them.memsql: Stores metadata local to a given node, including which local databases exist, which local users exist, etc.
Other than information.schema, these databases are not intended for users. Some commands are not allowed for these databases. For example: ATTACH / DETACH DATABASE, BACKUP DATABASE, DROP DATABASE, REPLICATE DATABASE, REBALANCE PARTITIONS, RESTORE REDUNDANCY.